Declassified 1991 Los Alamos report on the need for tactical nuclear weapons to provide CREDIBLE deterrence of Russia in the post-Cold War era, to avoid the 1930s style appeasement culture that encourages enemy coercion, aggression and finally a World War:

Joseph S. Howard, II, and Edward I. Whitted, “The Future of Non-Strategic Nuclear Forces; are these capabilities still needed”, report LA-12063-MS, April 30, 1991, originally classified Secret – Formerly Restricted Data, Nuclear Weapon Data, Sigma 3. Vital extracts:

Page 7: “Executive Summary … [tactical nuclear weapons are vital]

“ * As a deterrent to future non-superpower nuclear-capable adversaries in a proliferated world. 

“ * As a deterrent to regional Soviet or Russian aggression as long as resurgence or reconstitution remains feasible. …”

Page 16: “Deployment of nuclear weapons to Europe created an extended deterrence umbrella for conventional force deficiencies. … The US, after fighting a war against totalitarianism, turned to a grand strategy of containment of Soviet imperialism. … therefore, the NATO alliance was formed to draw the line against further Soviet expansion.  Unfortunately, the Soviet Union and its Warsaw Treaty Organization (WTO) alliance deployed forces far beyond those required for its own defense.  Unable and unwilling to match the conventional force goals of the 1952 Lisbon Conference, the US deployed its first theatre nuclear weapons for NATO in 1953.  Over the past 45 years, NATO nuclear doctrine has evolved from ‘massive retaliation’ in MC 14/2, to ‘flexible response’ in MC 14/3, then to the development of provisional political guidance (PPG) for initial and follow-on nuclear use … now to the proposed ‘weapons of last resort’ … the presence of theatre nuclear weapons (now NSNF) gave an aura of credible response options before the ultimate response.”

Page 18: “The presence of NSNF in Europe contributed to the long peace of 45 years.  These weapons helped to DETER the Soviet Union from initiating nuclear coercion or overt aggression against the NATO alliance. … We argue that the existence of theatre nuclear weapons was a major factor for the past 45 year peace in Europe.  Prior to the stabilizing effects of NATO, due in part to its nuclear weapons, the European continent had been the scene of several major wars and periods of crises, largely stemming from rampant nationalism [no, invading over countries is socialist imperialism, not nationalism, and expansionist socialism is the OPPOSITE of nationalism, it is dictatorial socialism where one group tries to create a world government akin to the Roman Empire, USSR, or EUSSR; truly nationalist countries are concerned with their OWN AFFAIRS, not with invading other countries for Marxism or Nazi Liebestraum].  The strategies of NATO worked.  They worked in spite of ambiguities in NATO declaratory policies; ambiguities necessitated by political constraints and public acceptability. … But it all worked to keep the peace.  The US policy of extended deterrence within NATO’s nuclear declaratory and operational strategies made the cost of aggression too high to Soviet leaders.  These weapons engendered cautious behavior. …”

Page 21: “A future nuclear-proliferated world would present enormous challenges to US defense interests. … Several of these nations maintain profoundly hostile relations to the US. … a future resurgent and mobilized Soviet Union remains feasible.  While intentions can move towards amicability, they can subsequently be reversed … the greater Russian Republic, should some republics become autonomous, may have future cause to counter US vital interests … Therefore, we are incredulous of US forces without NSNF [tactical nuclear weapons] to prevent war or to terminate war against hostile nuclear-armed states.  The rationale for NSNF must rest upon its capabilities to deter a plausible resurgent Soviet Union, or any of several regional powers with potential nuclear capabilities.  As NSNF kept the long peace in Europe because it engendered cautious behavior, so should NSNF be kept as an incalculable risk towards any nuclear state contemplating aggression.

“The rationale for NSNF [tactical nuclear weapons] also involves the element of credibility: the NCA should have options other than central strategic forces for an appropriate response.”

Page 27: “Credible deterrence necessitates WILL to employ nuclear weapons as expressed in declaratory strategies and roles, and effective military CAPABILITY.”

Page 32: “Based upon IC projections we assumed … three future regional threats …

“ 1. Reconstituted Soviet Union or greater Russian Federation. …

“ 2. Pacific Basin, regional nuclear adversary, e.g., North Korea …

“ 3. Middle East, regional adversary, e.g., federation of Iran and Iraq [currently IS, Islamic State]…

“… It is not necessary for our purposes to spell out the road to crisis or to war.  It might be a future combination of nuclear coercion, renewed interest in East European domination, oil proclivities towards the Middle East, or others.”

Further discussion: http://glasstone.blogspot.co.uk/2014/08/is-new-islamic-state-in-middle-east.html